This invention relates to the field of ultrasonics and, more particularly, to ultrasonic transducers for generating and detecting acoustic wave energy.
Ultrasonic techniques have become increasingly important in recent years in many different applications. In materials science, for example, evaluation procedures utilizing ultrasonics have been advantageously employed in nondestructive testing.
In order to utilize ultrasonic energy to interrogate a material, some means must be employed to generate ultrasonic waves within the material. In the past, ultrasonic transducers which operated by virtue of the piezoelectric principle have been used. More recently, however, new ultrasonic transducer designs have been developed with improved performance and increased flexibility of operation. These new transducers, known as electromagnetic acoustic transducers (EMATs), are more versatile than prior art designs because they need not be maintained in physical contact with an object to generate an ultrasonic wave therein. Furthermore, EMATs are capable of operating at high speeds and in adverse environments, such as high temperature.
The EMAT designs which are known in the art, however, exhibit some disadvantages in operation as compared to other transducer types. EMATs tend to exhibit relatively high electrical losses and high electrical impedance, as compared to prior art transducers, properties which may make it more difficult in some applications to generate an ultrasonic signal of sufficient amplitude with this type of transducer.
Therefore, a need has developed in the art for an improved electromagnetic acoustic transducer which operates with lower electrical losses and exhibits a relatively low electrical impedance.